A study was made with Yellow A. B. (l-phenylazo-2-naphthylamine) because this oil-soluble coal tar dye is extensively used in this country to color foodstuffs. The daily ingestion of large amts. of Yellow A. B. (each animal consumed 8-12 mg. of the dye daily) failed to produce liver tumors or cirrhosis in rats during 50 to 528 days'' feeding.